Udzungwa red colobus, Piliocolobus gordonorum
UDZUNGWA RED COLOBUS
Piliocolobus gordonorum
Geographic Distribution and Habitat
The Udzungwa red colobus, also known as the Uzungwa red colobus and the Iringa red colobus, is found exclusively in the forests situated along rivers or within the mountainous terrain of the Udzungwa Mountains in the Iringa Region of south-central Tanzania. They are found at elevations of 0.12-1.37 miles (200-2,200 m) above sea level and are less abundant at higher elevations.
Size, Weight, and Lifespan
The head-body length of male Udzungwa red colobuses ranges between 18.1-27.6 inches (46-70 cm), while females have a head-body length ranging between 18.5-24.4 inches (47-62 cm). The tail ranges from 21.7-31.5 inches (55-80 cm) among males and 16.5-31.5 inches (42-80 cm) among females. The tail of males is also generally thicker, and more heavily furred compared to that of females. Males weigh between 19.8-28.7 pounds (9-13 kg), while females weigh between 15.4-19.8 pounds (7-9 kg). Males being slightly larger than females, having longer canine teeth when compared with those of females, along with the previously-mentioned differences between tail characteristics, are all examples of sexual dimorphism, or noticeable physical differences between genders.
The lifespan of the Udzungwa red colobus is unknown, however, their closest living relatives have lifespans ranging between 20 and 30 years old.
Appearance
The most striking feature of the Udzungwa red colobus is the red-orange cap on the top of the head. This auburn tuft of hair provides a stark contrast to the rest of the body, which is black on the backside, and white along the belly, sides of the head, and inner portions of the limbs. Their faces, which come with dark brown eyes, are covered by mostly black skin and patches of pink scattered on the muzzle.
All colobus monkeys lack true thumbs, and where the thumb would be, there is only a small nub. However, colobus monkeys make up for this with the remaining four hook-like fingers on each hand. This hand structure actually makes it easier for colobus monkeys to swing from branch to branch in quick succession. These guys certainly aren’t handicapped!
Their long tails are non-prehensile, meaning they are not used for grabbing or grasping, but rather to maintain balance when walking along branches in the trees.
Diet
Leaves make up the majority of the Udzungwa red colobus’s diet, consisting of up to 71%! The remainder of the diet is made up of fruit, seeds, flowers, buds, and rarely, lichen, and dirt. An animal such as the Udzungwa red colobus, who primarily consumes leaves, is known as a folivore.
Why eat dirt? It is believed that this aids in digestion! The Udzungwa red colobus has a large, four-chambered stomach, which allows for the digestion of the large amounts of cellulose found in their leafy diet. This cellulose-rich diet, however, takes a long time to digest.
Behavior and Lifestyle
The Udzungwa red colobus is diurnal, being most active during daylight hours, and arboreal, preferring to spend most of their time in the trees. Colobus monkeys are in fact, said to be the most arboreal of all African primates! They only leave the trees when it is absolutely necessary.
The metrics of their activity budget are limited, but of the time observed, 38% is spent on foraging. The Udzungwa red colobus is awake for ten hours of the day, during which seven of those hours are spent lazing around and resting as they digest the large amounts of cellulose found in the leaves they consume. Other activities this red colobus species engage in include social activities such as grooming and traveling around their habitat.
Rather than build sleeping nests, Udzungwa red colobuses sleep high up among the branches of tall trees.
Besides humans, predators of the Udzungwa red colobus include birds of prey such as the crowned eagle. When a predator is nearby, the males will gather together to defend the group, while the females, infants, and juveniles, escape to safety. Many other species of red colobus monkey are seriously threatened by rising hunting rates from chimpanzees; however, the isolated Udzungwa red colobus lives well outside of the chimpanzee’s current range.
What’s in a name?: The word “colobus” comes from the Greek word meaning “cut short” or “maimed,” in reference to their lack of a thumb.
🎵 I always feel like somebody’s watching me 🎵 (Thanks for the lyrics, Rockwell): Udzungwa red colobuses are often suspicious of newcomers. So before a single monkey joins a new group, an individual can spend several months tracking and spying on their potential new family to see if they will one day be accepted.
Udzungwa red colobuses live in multi-male multi-female groups of typically 21-40, averaging 24 individuals, but may range from anywhere between 7 and 83 members. According to a 2004 study, groups are smaller in forests that are “small” (considered less than 1.93 square miles (<5 km²)), dominated by deciduous trees, and/or are heavily degraded by human activities. This is compared with those living in “large”, intact, and relatively mature blocks of moist, mixed evergreen and semi-deciduous forest. What do all of these forest-related terms mean? Deciduous trees lose their leaves during the autumn and winter months and regrow them in spring, while, as evident by their name, evergreen trees keep their leaves year-round.
Around sunrise, the colobus group awakens and forages during the early morning. They rest for most of the day, and spend much of their downtime grooming one another and building social bonds. They forage again in the evening before retiring for the night. All red colobus species often sleep in the same trees in which they were feeding that day, preferring to stay in the tallest trees that they can find.
Upon reaching maturity, male red colobuses tend to stay in their natal group for life and develop strong social bonds with one another. They usually only leave the group in order to form a group of their own. Females in the main group often form smaller associations and will move from group to group several times during their lives.
The home range of a group of Udzungwa red colobuses ranges between 62-247 acres (25-100 ha). All red colobus species are fiercely territorial, and they often engage in violent battles with neighboring troops. Most of this fighting is left to the males, who also fight among members of their own group in order to rise up within the dominance hierarchy.
Finally, with regard to associating with other primates, the Udzungwa red colobus has been seen going about the day alongside Angolan colobuses (Colobus angolensis), kipunjis (Rungwecebus kipunji), Sanje mangabeys (Cerocebus sanjei), Sykes’ monkeys (Cercopithicus mitis albogularis), and yellow baboons (Papio cynocephalus).
The Udzungwa red colobus has a fairly wide vocalization repertoire. However, most of the vocalizations remain unknown to science in terms of usage, and more research is needed. “Chist” calls are given by adult males, adult females, and juveniles, to human observers. Barks, yelp-barks, yelps, wheets, shrill squeals, shriek-sqwacks, quavers, and sneezes have also been observed, but their function(s) are not yet known.
Besides these vocalizations, grooming is used to strengthen bonds and rid fellow group members of parasites.
Udzungwa red colobus monkeys breed year-round, and mating is most frequent between March and June. Males compete with one another for mating opportunities, but no male holds exclusive rights. A female’s anogenital region will swell up when she is receptive, and after breeding, she is pregnant for around six months. She gives birth to a single offspring, and on average will give birth every three years.
As mentioned previously, females move between groups several times during a lifetime. Due to this, most females in a group are unrelated to one another. Scientists speculate that this is why red colobus mothers do not generally practice allomothering, in which all females work together to raise the offspring. Instead, mothers are highly protective of their young from all members of the group.
Females reach sexual maturity at two years of age. At that point, they may go off on their own to find a new group or they may stay close to their mother and aunts and leave only when they do. Males reach sexual maturity some time between three and four years of age, and for the most part, stay in their natal group.
As a portion of their diet consists of fruit and their seeds, Udzungwa red colobuses aid in the regeneration of their forest habitats by dispersing seeds through their feces as they travel throughout their habitat. In addition, by feeding extensively on young leaves, they largely strip trees of these leaves. This stimulates the trees to recover by producing a new set of young leaves, thereby increasing their productivity and growth rate. They also play a role in pollination. Like bees and butterflies, they collect pollen from flowers when consuming them. They then deposit the pollen on each subsequent flower they visit, thereby pollinating the plants. Finally, as a prey species, they also play a role in feeding local predators within their range.
The International Union for Conservation of Nature lists the Udzungwa red colobus as Vulnerable (IUCN, 2016), appearing on the IUCN Red List of Threatened Species.
The primary threats facing the Udzungwa red colobus are illegal hunting for local and national meat trade and consumption, and habitat loss due to logging, conversion to agriculture, firewood collection, and charcoal production.
The Udzungwa red colobusis listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
Presently, around half of the Udzungwa red colobus’s range within the Udzungwa Mountains National Park is effectively protected. The remaining habitat is in forest or nature reserves or is not protected, as it is on public land. The Udzungwa red colobus is only nominally protected by law in Tanzania as “Presidential Game”. Better enforcement of these laws is essential in areas where the colobus is hunted.
Conservation priorities for the Udzungwa red colobus include:
• Greatly improved management of forest and nature reserves outside of the Udzungwa Mountains National Park
• Clarification of the conservation status of Magombera Forest, a lowland forest at the foot of the Udzungwa Mountains. This would include the provision for effective management and the assignment of formal and on-the-ground protection to this forest
• Fire prevention to promote forest expansion and establishment of corridors among forest blocks, thereby allowing forest-dependent species such as the Udzungwa red colobus to disperse and thrive
• On a more general scale, improvement of law enforcement in order to prevent poaching, fires, encroachment and illegal logging
Along with these crucial priorities, additional research on the Udzungwa red colobus’s population size, distribution, and trends, along with further monitoring of their population trends over time, are also necessary in order that this endearing colobus species survives the looming threat of endangerment and extinction.
- https://www.alltheworldsprimates.org/Members/Home/MasterPrimate.aspx?tid=1222
- https://www.bioexplorer.net/animals/mammals/monkeys/udzungwa-red-colobus/
- https://en.wikipedia.org/wiki/Red_colobus
- https://en.wikipedia.org/wiki/Udzungwa_red_colobus
- https://www.gbif.org/species/4266998
- https://www.iucnredlist.org/species/40015/92629595
- https://www.researchgate.net/profile/Andrew-Marshall-29/publication/306065366_Udzungwa_Red_Colobus_Piliocolobus_gordonorum_Matschie_1900/links/59e328880f7e9b97fbeaba66/Udzungwa-Red-Colobus-Piliocolobus-gordonorum-Matschie-1900.pdf
- https://www.tfcg.org/what-we-do/conserve/magombera-forest/
- http://www.udzungwacentre.org/documents/Reports/Rovero_2009_JAS.pdf
- https://wildark.org/species/udzungwa-red-colobus/
- https://zoogalaxy.net/en/photos/mammalia/primates/catarrhini/colobinae/piliocolobus/piliocolobus-gordonorum
Written by Sienna Weinstein, January 2025